Structure—performance relationships of viscosity index improvers: I microstructural determination of olefin copolymers by NMR spectroscopy

Abstract

Five commercial olefin copolymer (OCP) viscosity index (VI, improvers have been characterised at the molecular level. The copolymer compositions have been determined using ' H a n d 13C-N M R spectroscopy. The microstructural parameters, such as cornonomer sequence distribution, number average sequence lengths and run number, have been determined by 13C-NMR spectroscopy. N M R spectral editing techniques, e.g. Distortionless Enhancement via Polarisation D-ansfer (DEPT) have been used for peak assignments. This analytical approach aims at correlating the microstructural parameters with the physical properties and performance of these VI improvers, to be communicated later.A viscosity index improver is an oil soluble polymer that significantly alters the oil viscosity, increasing its effect with temperature. This type of polymer, in addition, makes the thickened oil non-Newtonian. The degree of non-Newtonian behaviour imparted to an oil is another important characteristic of the polymer in relation to its effectiveness as a VI The effective viscosity of a lubricant in critical engine areas influencing key performance characteristics is a function not only of shear rate, but also of the response of the particular polymer VI improver's chemistry and constitution, to the shear rate and t e m p e r a t~r e .~~?~ An important class of VI improvers is that of olefin copolymers, primarily derived from ethylene and propylene comonomers. The chemical and associated physical characteristics which make these copolymers most suitable for use as VI

Synthesis and Evaluation of Some Polymers as Lubricating Oil Additives

“…Performance of viscosity index improvers depends on the behavior of the polymer molecules in the oil, polymer solubility, molecular weight, and resistance to shear degradation are the most important parameters. [7] The polymer molecule in solution exists as random coil, [8] which is swollen by the lube oil solvent. Polymer solubility generally increases with increasing temperature, as the polymer molecule change from tight coils to an open configuration, which has a greater volume; this increasing in volume causes an increasing in the viscosity of the lube oil, which offsets the normal reduction in viscosity with increasing temperature.…”

Deformulation of metalworking lubricants: Organic phosphorus additives characterization by 1H, 13C and 31P NMR

“…A particular care will be devoted to the additives which have considerably improved the properties of lubricants and their performance in service during these last ten years: the wetting agents [5], the extreme pressure additives [6] and the macromolecular compounds [7].…”

Problems, trends and prospects for present-day automative engine oil formulations

“…These additives have to meet the following requirements: thickening ability (a low polymer treat rate, < 1.0 %), viscosity temperature relationship ability (a low thermodynamic parameter of viscosity flow for oil solutions, a high viscosity index, > 120), high shear stability (after Bosch injector test oil is within viscosity grade), stability to temporary viscosity loss (oils of newtonian viscosity mode are preferred) and sufficient thermooxidative stability. Viscosity modifiers exhibiting dispergating ability are desirable [119][120][121][122][123][124]. Additives on the base of ethylene--olefins and hydrogenated styrenediene copolymers in which ethylene moieties comprise ³70 % largely meet these requirements (M n = 5.000-30.000, M n /M w < 4, [h] = 1.3-1.8 dl/g, index of shear stability < 18 %, melt point < 303 K).…”